Power semiconductor switch devices, like power metal oxide semiconductor field effect transistors (MOSFETs) or insulated gate bipolar transistors (IGBT) are used to switch high voltages and/or currents. For example, in the automotive field such power semiconductor switches may be used to selectively couple an electric motor with supply voltages in the order to some hundreds of volts, with corresponding high currents of the order of above 10A. In case of a short circuit occurring e.g. in a load coupled to the switch, due to the high voltages extremely high currents may flow, which may damage or even destroy the semiconductor switch device. Therefore, it is desirable to detect such short circuit conditions and take appropriate steps, for example open (switch off) the semiconductor switch device thus interrupting any current flow.
Conventional approaches use a desaturation behavior of the semiconductor switch device to detect short circuits. Desaturation behaviour in the context of this application means that the semiconductor switch is limiting a current flow through load terminals of the semiconductor switch and at least a major portion of a supply voltage drops across the load terminals of the semiconductor switch. However, this approach is not suitable for all semiconductor devices and short circuit situations.